The present invention relates generally to a method of detecting trivalent chromium Cr(III), and particularly to a method of detection using atomic spectrometric methods without pre-concentration or preliminary separation from chromium in other valence states.
The chemical speciation of trace elements in samples is very important because their chemical forms generally influence the effects that such trace elements (especially trace heavy metals) have on ecological and environmental systems. Some elements in a sample may be present in more than one valence state, as well as cationic, anionic and neutral species. The increasing demand for speciation information from a particular sample arises from the understanding that the toxicity of a given element critically depends on its actual present chemical form. The different oxidation states of chromium is of critical concern. Trivalent chromium Cr(III) is considered a trace element essential for the proper functioning of living organisms. On the other hand, hexavalent chromium Cr(VI) presents the possibility of toxic effects on biological systems.
Chromium is commonly used in various industries, and may be released in a considerable amount into the environment. Cr(VI) may be transformed into Cr(III) by various means (chemical and/or biological). Accurate speciation information would be useful in assessing the impact of releases to, the environment and the effectiveness of remediation efforts.
There are various known techniques for speciation determination of chromium, including Electron Spin Resonance (ESR) spectrometry, ion chromatography and high-performance liquid chromatography (HPLC), that are often coupled with sophisticated detection systems like inductively coupled plasma atomic emission or mass spectrometry. However, these procedures do not satisfy all requirements for routine analysis mainly because of their complicated process design, time consumption or the need for expensive instruments.
Atomic absorption spectrometry (AAS) is the key technique for the determination of total chromium. Among AAS techniques, flame atomic absorption spectrometry (FAAS) is preferred because it is simple and inexpensive. Efforts to determine trace metals directly and reliably by FAAS are usually limited owing to the low concentrations of analytes and matrix interferences. To enhance the sensitivity and the precision of the method, pre-concentration and separation techniques, such as co-precipitation, liquid—liquid phase extraction, ion exchange and recently, solid-phase extraction are most frequently used.